Saddleman Tail Bag for your Sportbike

I definitely see the value in a tailbag that has top access, since my Kriega packs don't. 

This Saddlemen Sport Tunnel Tail Bag looks like a cool tailbag if you have a tiny rear seat like on a Speed Triple, Daytona 675 or similar. A customer came in recently and purchased one for her Daytona 675. It looks like the straps work under the seat so if you don't have any mount points below, this should work well.

Another bag I recommend for top access is the Cortech Super 2.0 Tail Bag (available in 14L or 24L), but you do need external mount points to attach this to your seat. Cortech also offers an optional rain cover if you choose the larger 24L option.

Tankbag Alternative, Giant Loop Zigzag Handlebar Bag

To prepare for our first ride across PA, the man wanted something smaller than a tank bag, but not a tank bag. He found this on Revzilla.com (there's always SO much stuff on that website :P) by Giant Loop, the Zigzag handlebar bag. I love their description at the bottom: FITS THESE MOTORCYCLE MAKES & MODELS
• BMW, KTM, Honda, Suzuki, Yamaha, Kawasaki, Ducati, Husqvarna, Triumph
• JUST ABOUT ANY MOTORBIKE

Indeed, it fit his S3 perfectly. It doesn't take up much space, you can barely see it here on his bike (right):

Best Backpack for your Motorcycle?

Maybe. The Kriega US25 is right in the middle of the Kriega lineup at 25 Liters. It's not waterproof, but it offers a nice midsize that doesn't feel too big on my frame. I always feel like a little kid if I wear something that's way too big on me. I just bought this last week and will be commuting with her to see how it feels on the bike. Click here for a full overview of specs and features. $189.